Monthly Archives: February 2017

A Sub-Synchronous Oscillations Study for a Wind Farm

Due to the recent sub-synchronous oscillations (SSO) events, most independent system operators (ISO) require a study that demonstrates immunity of wind projects with respect to SSO prior to energization. For this study, we consider a wind project sited in proximity of a series compensated transmission line, where it becomes radially connected under certain N-1 conditions.

Using a frequency scan screening and a detailed electromagnetic transient (EMT) study we show that the project is immune to SSO. However, the EMT results show that clearing a fault on the transmission line that leads to a radial connection of the wind project to the series compensated transmission line causes the project to trip offline due to voltage and reactive power issues stemming from the proximity of the project to the series capacitor bank but not due to SSO. We conclude that the impact of proximity of series capacitors and wind projects need to be investigated beyond SSO for reliable operation of the grid. Index Terms—Sub-synchronous oscillations, Electromagnetic transients, frequency response, wind farms, series capacitors

A Reduced Order Model for a TOV Study in a Solar PV Project

Special system studies are needed to assess the different preliminary designs of solar photovoltaic (PV) projects. One of these is a Temporary Overvoltage (TOV) study. The main purpose of a TOV study is to evaluate the capability of the surge arresters (SAs) within the substation.

To assess the capability of the SAs accurately, a detailed electromagnetic transient (EMT) model of the project has to be built. With the detailed EMT model, which has a large number of inverters, the run time of the model becomes prohibitive even for a single scenario. In this paper, we propose a method to systematically reduce the order of the EMT model at the substation level thus making the model suitable for TOV studies. The response of the reduced order model is then benchmarked against the response of the full order model of an 80 MW solar PV project for various TOV scenarios. Simulation results show satisfactory agreement between the response of the detailed model and the response of the reduced order model. Additionally, the run time of the proposed reduced order model is less than the run time of the full order model by a factor of ninety six.